From what I can gather the "sun" is low and behind the specular sphere that has the letters inside and the camera is not inside the sphere
If one were to replace the "sun" with a mesh emitter and placed it behind the sphere can you get the same result? I tried it but my scene went black but there were one or two pixels of light specs... so it was trying to do something. If it is user error thats ok... but if it only works with daylight I might as well know now

Same with HDR environment if the light source in the image is placed in the correct place... can it create the rays? ( I tried quickly but was not able to but figured I might be doing it wrong.
Thanks for any info on this feature. Have always loved that effect through the clouds in real life. Just working on understanding how it should be set up.
Thanks